mercruiser spark plugs ! to change or not to change, that is the question !

[lakeerieboater26]

Boat runs fine, but plugs look a little dirty. Plugs are 5-10 years old. not really sure. Should I replace them to prevent any issues out on the water and would new ones possibly give me better performance ? if so, what kind should i get and is it .035 or .045 for the gap ? or just leave it alone ?

 

[proxyx]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

replace one and see what happens, if this cylinder runs faster then others replace them all

but seriously: your call, 5 or 10 years? small difference
if not eaten away, corroded, broken, only dirty... clean them well, boats run way less hrs/year then cars so plugs should last longer
no clear answer

 

[Bondo]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

Ayuh,... Believe it or Not,... Mercruiser has used Many motors over the years....
Which 1 are you talking about,..?? What Vintage,..??

 

[a70eliminator]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

Who cares, it's a spark plug, he's more than likely in need of a complete tune up, whatever engine it is, to change or not to change that was the question, personally I do a seasonal inspection and cleaning, I think replacing plugs yearly is not necessary but some prefer to change them if for nothing but peace of mind.

 

[Bondo]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

if so, what kind should i get and is it .035 or .045 for the gap ?

Who cares, it's a spark plug, he's more than likely in need of a complete tune up, whatever engine it is,

Ok,... Then You tell him Which plugs,+ What gap....
As you see,... It Does matter....

 

[lakeerieboater26]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

its an alpha 1, 3.0, Gen 1

 

[proxyx]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

ac mr43t (merc recommended)
ngk br6fs (I like/use those)
champion rv8c

I have them at 0.035 if I recall correctly.
Rockauto.com may be a good/inexpensive source.

 

[Simoniz]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

Who cares, it's a spark plug, he's more than likely in need of a complete tune up, whatever engine it is, to change or not to change that was the question, personally I do a seasonal inspection and cleaning, I think replacing plugs yearly is not necessary but some prefer to change them if for nothing but peace of mind.

As you mentioned that its a 3,0l model, you should at least get the rear spark plug out as soon as you can and be gentle with it when you remove it.

On this engine in some applications (Bayliner 175 is one) condensation gathers round the No 4 spark plug in the recess in the cylinder head and corrodes the plug.

Then, as happened to me, you'll be out boating one day and there'll be a bang as if a bomb has gone off followed by a loud chuffing sound when the rusted through plug blows out of the cylinder head. Then you're left hoping that you can get the remaining thread portion out with an easy out.

 

[TowRoper]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

it does not mater what engine it is? ARE YOU KIDDING ME! glad you don't do my engine work! but then again the things you do keep me in business lol

 

[Apollo75]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

Hello;

Look at the electrode --- the middle part of the bottom end of the plug where the spark leaves and jumps to the grounding electrode "the bent part" and see if it is rounded, eroded, worn etc. You can file it down and make it square again, regap the plugs and use the plugs or keep them in the boat in case of one of the new plugs miss fires.

It all depends on how many hours are on the plugs and if they are still firing. It is a spark plug --- either needs replacing or doesn't. Most people replace these things for piece of mind and throw away good slightly used plugs.

OFM

 

[artificialreef]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

are'nt these things like 3 bucks each? I wish this was my only problem!

 

[gadget73]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

I replace mine usually every 2 years. If I notice any improvement in how it runs, it tells me I was overdue for a plug change. Thats just me and my slightly excessive repair/replacement schedules though. At 5+ years old, those plugs would have been in the trashcan at first oppertunity. I'd also pop the distributor cap and give it a good looking over, and inspect the plug wires for any signs of burns or cracks. Any damage or signs of excessive wear and those parts would be replaced. Also, if you've not done so recently, the fuel filter should be replaced. I do those every year.

As for plug type and gap, I've had good luck just using the Merc reccomended stuff. If its not marked on the engine somewhere, then the manuals are probably available in the sticky at the top of this forum.

 

[Apollo75]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

Years ago in my GTO with milled heads and 12.5 to 1 compression and more Carb than most --- plugs fouled quickly.

It depends how you use your boat --- I troll a lot and that usually does not foul plugs with an inboard or new outboard --- and I move from one part of the lake to another at medium speed 3000-rpm. So, my plugs last at least three years as I do not put a lot of hours on my boat as the season is short in Idaho for water sports and I do not like fishing freezing my *alls off.

I know other parts of the country have nice weather all year long and people use there boats many more hours a season than I do.

I am one to check things before I change them --- I do think I am going to start changing my impeller every two years or take it out completely while it is sitting in storage for 6-months of the year, and my fuel filter every season

Maybe I need to get on a schedule

OFM

 

[a70eliminator]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

I didn't get past the should I or shouldn't I replace the plugs.

excuuuse me

 

[dgopetactical]

Re: mercruiser spark plugs ! to change or not to change, that is the question !

are'nt these things like 3 bucks each? I wish this was my only problem!

OH-BOY, your not kidding there!!!!! if plugs were my only issue I would do the polka Auto-zone has champions on sale for 99 cents each. Change the plugs and do a COMPLETE tune up.
I change mine every spring just because i feel its the right thing to do my choice my $$. 5-10 years?? not me. Don recomends changing them every year in his sticky and from his track record i will listen to that advise!!
Denny